The growth and development of plants mainly relies on sunlight. But for other commercial crop such as vegetables, flowers and medicinal plants, their industrialization and tissue culture still needs artificial light. Especially when light application time is very short in late Autumn, Winter and Spring, it will lack of light seriously inside greenhouses and crops can't grow up normally, which would become worse in case of continuous cloudy day, greasy weather and rain and snow day. Therefore, artificial lighting, as a direct light supply inside greenhouses, is an efficient way to promote the growth of plants. And the theoretical basis on efficient and energy-saving supplementary light for plants is mainly from the theory that plants will absorb the light selectively. In recent years, people are working hard on simulating the absorption spectrum of plants so as to develop a kind of light source, by which its emission spectrum will approximate to the absorption spectrum of plants to the hilt to realize a resonance absorption and higher efficiency of photosynthesis.
In one hand, with hundred years of the technology on tissue culture of plants, the research on industrialization of important commercial crops is still in the ascendant by this technology. In the other hand, the improvement on artificial lighting for tissue culture of plants mainly concerns on cost-saving artificial light with lower heat elimination and high efficiency, which is suitable for growth of plants. At present, artificial lights used for tissue culture of plants in our country are mainly provided by filament lamp, fluorescent lamp, sodium lamp and high pressure mercury lamp and so on. However, the emission spectrum of these artificial lights can not satisfy the selective requirement for the growth of plants, and improve low efficient supplemental light, short service life of fluorescent tube and low luminous efficiency, great heat productivity of fluorescent tube which asks for extra electricity, and thus it leads to high cost of power consumption.
It is proved by the preliminary study of LED light source at abroad and Taiwan that LED light source can be used as artificial lighting inside greenhouses so as to enhance growth and quality of plants. Compared with traditional artificial lighting, features of LED include adjustable light intensity, light spectrum, low cooling load, high electro-optic conversion efficiency, small volume, long service life, using direct current and setting of special wavelength, fixing of wavelength etc, without harmful gas or with good performance on environmental protection, and thus LED is an artificial lighting system quite suitable for tissue culture of plants.
Dendrobium candidum, ornamental dendrobium and phalaenopsis and other orchids take important position in medicine and flowering plant industries of our country, and as the economics develops quickly, their and scale and production value will have further increase and improvement. Based on analysis of current production status, there are few problems to be solved urgently in the period of seeding and breeding of orchids. The first problem is high consumption of energy, which will lead to high production cost; the second problem is long cycle of seeding and breeding, difficult to satisfy the culture requirement of farmers. Due to limitation of technology, currently it lacks of LED lighting directly used for orchids, especially for tissue culture of dendrobium candidum, ornamental dendrobium and phalaenopsis. 